Balancing of multi-stage pump using the coupling hub

In this paper, we present an investigation to perform a temporary on-site balancing of machines which rotor is not accessible, such as multi-stage oil centrifugal pumps, in order to bring back the vibration magnitude below the alarm threshold, waiting for the scheduled general review of the machine. We have shown that if the vibration measured on the Driver End Support (DE) is very higher than that measured on the Non Driver End Support (NDE), we can consider the Coupling Hub fitted to the Pump (CHP) a correction plane in order to apply on site balancing by means of the Influence Coefficients Method. This permits to overcome the problem of the inaccessibility of the rotor and to solve, in the shortest possible time, the unbalance occurred during the working. We have experimentally verified this hypothesis in a multistage pump of a petroleum industrial plant by two different approaches. The first performs Single Plane Balancing (SPB) and vibration measurements on two supports, acquired with eddy probe sensors. The second approach, which may be more simple and easy to apply, aims to apply the SPB using vibration measurements on only one support acquired with an accelerometer. The results of the different approaches have been compared.